Which term describes the four modes of opposition in standard lists?

• A. subalternate
• B. equivalence
• C. contradiction
• D. contrariness

Answer: (B)

In standard lists, how two propositions relate in truth value is described by opposition relations, forming the square of opposition. There are four distinct connections: contraries (two universal propositions of opposite quality cannot both be true but can both be false), subcontraries (two particular propositions of opposite quality cannot both be false but can both be true), contradictories (direct negation where one is true exactly when the other is false), and subalternation (truth flows downward from a universal to a particular of the same quality). Taken together, these describe the whole family of opposition relations. Equivalence, by contrast, concerns two statements sharing the same truth value, which is not what these opposition relations specify. So the four modes are best described as opposition relations within the square of opposition, not equivalence.